Connected: An Internet Encyclopedia
RFC 1771 - 9.1.3 Phase 3: Route Dissemination

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### 9.1.3 Phase 3: Route Dissemination

The Phase 3 decision function shall be invoked on completion of Phase 2, or when any of the following events occur:

1. when routes in a Loc-RIB to local destinations have changed

2. when locally generated routes learned by means outside of BGP have changed

3. when a new BGP speaker - BGP speaker connection has been established

The Phase 3 function is a separate process which completes when it has no further work to do. The Phase 3 Routing Decision function shall be blocked from running while the Phase 2 decision function is in process.

All routes in the Loc-RIB shall be processed into a corresponding entry in the associated Adj-RIBs-Out. Route aggregation and information reduction techniques (see 9.2.4.1) may optionally be applied.

For the benefit of future support of inter-AS multicast capabilities, a BGP speaker that participates in inter-AS multicast routing shall advertise a route it receives from one of its external peers and if it installs it in its Loc-RIB, it shall advertise it back to the peer from which the route was received. For a BGP speaker that does not participate in inter-AS multicast routing such an advertisement is optional. When doing such an advertisement, the NEXT_HOP attribute should be set to the address of the peer. An implementation may also optimize such an advertisement by truncating information in the AS_PATH attribute to include only its own AS number and that of the peer that advertised the route (such truncation requires the ORIGIN attribute to be set to INCOMPLETE). In addition an implementation is not required to pass optional or discretionary path attributes with such an advertisement.

When the updating of the Adj-RIBs-Out and the Forwarding Information Base (FIB) is complete, the local BGP speaker shall run the external update process of 9.2.2.

Next: 9.1.4 Overlapping Routes

Connected: An Internet Encyclopedia
RFC 1771 - 9.1.3 Phase 3: Route Dissemination